add check to opensfm BA that GPS accuracies are positive

Summary: For MLY internal we sometimes get -1 values for GPS accuracy. The new EXIF parser now prevents this from happening and sends None instead, but this diff adds an error message for this case so that we immediately notice if this ever happens again.

Reviewed By: DodgySpaniard

Differential Revision: D58373009

fbshipit-source-id: 526d92fbec49be7a9a8398648d722880ab138d54

opensfm/src/sfm/src/ba_helpers.cc

@@ -8,6 +8,7 @@
 #include <chrono>
 #include <cmath>
 #include <stdexcept>
+#include <string>
 
 #include "geo/geo.h"
 #include "map/defines.h"
@@ -672,6 +673,11 @@ py::dict BAHelpers::Bundle(
         const auto pos = shot.GetShotMeasurements().gps_position_;
         const auto acc = shot.GetShotMeasurements().gps_accuracy_;
         if (pos.HasValue() && acc.HasValue()) {
+          if (acc.Value() <= 0) {
+            throw std::runtime_error("Shot " + shot.GetId() + " has an accuracy <= 0: "
+                                    + std::to_string(acc.Value()) + ". Try modifying "
+                                    "your input parser to filter such values.");
+          }
           average_position += pos.Value();
           average_std += acc.Value();
           ++gps_count;